[IMP] accounting: default taxes in taxes.rst

Since https://github.com/odoo/odoo/pull/115222, a new line on an invoice
won't have the default sales tax put on by default. If there are no
taxes on the product, the account or from predictive, the tax will stay
empty. Its use has been restricted back to the tax put on new products.
It is still used in Accounting Firms mode, as we don't want people
to have to input the product when quick encoding.

task-3045026

closes odoo/documentation#4421

Signed-off-by: Castillo Jonathan (jcs) <jcs@odoo.com>

content/applications/finance/accounting/taxes.rst

@@ -13,11 +13,11 @@ supports all kinds of uses and computations.
 Default taxes
 =============
 
-**Default Taxes** define which taxes are automatically selected when there is no
-other indication about which tax to use. For example, Odoo prefills the **Taxes** field with the
-Default Taxes when you create a new product or add a new line on an invoice.
+**Default Taxes** define which taxes are automatically selected when creating a new product. They
+are also used to prefill the :guilabel:`Taxes` field when adding a new line on an invoice in
+**Accounting Firms** mode.
 
-.. image:: taxes/default-invoice-line.png
+.. image:: taxes/default-taxes-product.png
    :alt: Odoo fills out the Tax field automatically according to the Default Taxes
 
 To change your **Default Taxes**, go to :menuselection:`Accounting --> Configuration --> Settings